Digital printer positioning means



Oct. 11, 1966 .1. o. YEISER DIGITAL PRINTER POSITIONING MEANS 2 Sheets-Sheet 1 Filed Nov. 50, 1962 INVENTOR.

JOHN O. YEISER ATTORNEY Oct. 11, 1966 J. o. YEISER DIGITAL PRINTER POSITIONING MEANS Filed Nov. 50. 1962' 2 Sheets-Sheet 2 FIG. 2

INVENTOR. JOHN O. YElSER BY W A flu ATTORNEY United States Patent 3,277,817 DIGITAL PRINTER POSITIONING MEANS John O. Yeiser, Huntington Beach, Calif., assignor to Beckman Instruments, Inc., a corporation of California Filed Nov. 30, 1962, Ser. No. 241,413 13 Claims. (Cl. 101-93) The present invention relate-s to a digital printer and more particularly to an analog-to-digital printer which periodically records on a chart a digital indication of the value of an analog input signal.

In the past various arrangements have been proposed and utilized for printing numbers or characters indicative of analog or digital data. Numerous devices, such as electric typewriters and the like, are employed in digital data processing systems to print digital data. Although these devices may be adapted to receive analog data and print this data in digital form, such devices are extremely complex, large and costly. Smaller and less costly devices of this nature include printers which utilize printing mechanisms similar to those found in conventional adding machines. The latter devices, while less expensive than many printers, still are characterized by complex and costly mechanisms and circuitry.

Simpler arrangements have been utilized which include a type-wheel that is positioned by some type of counting mechanism or electronic follow-up system. An example of the latter apparatus may be found in US. Patent No. 2,668,870Ridler which relates to a printing telegraph receiver. As disclosed in this patent, a type-wheel is rotated from a given angular position and stopped by an electromagnetically actuated pawl after the type-wheel has rotated a desired number of character positions. A printing hammer then is actuated to print the desired character. Although this system is relatively simple, it is extremely limited in speed and accuracy. The latter is true since generally the type-wheel can only print one to two digits at a time, or if the type-wheel is made sufliciently large such that it can provide a greater number of digits, the time required for the type-wheel to reach the desired position is excessive for most applications.

Another arrangement which has been proposed in the past includes a mechanical counter driven by a servo system. Such mechanical counters which include at Geneva mechanism, or the like, cannot rotate at sufiiciently fast speeds in order to provide rapid printing.

According to a feature of the present invention, a digital printer is provided which obviates the difiiculties and limitations found in prior digital printers, and which is relatively simple and inexpensive.

Another feature of the present invention is the provision of a digital printer which receives an analog input electrical quantity and prints a digital representation thereof, and which includes coarse and fine print wheels each of which is moved to an analog position and subsequently moved to a digital position.

A further feature of the present invention is the provision of a printing device which includes a first printing mechanism that is positioned in accordance with an analog signal and then digitized, and a second printing mechanism which is positioned to an analog position while the first wheel is being digitized and is subsequently digitized.

An additional feature of the present invention is the provision of a printer in which a first printing mechanism is positioned in accordance with a variable input electrical quantity and then digitized during which time the first printing mechansm may be, and in general is, positioned to a second position in accordance with an increment of said variable input quantity, and a second printing mechanism is positioned in accordance with said increment and then digitized.

Another feature of the present invention is the provision of a digital printer which receives an analog input electrical quantity and prints a digital representation thereof, and which includes coarse and fine print wheels each of which is moved to an analog position and subsequently moved to a digital position, and which further includes a pen mechanism which is moved in accordance with the analog input quantity.

In an exemplary digital printer constructed in accordance with the teachings of the present invention, a first printing mechanism, which may take the form of a print wheel, and a second printing mechanism, which may take the form of a print wheel or a sector thereof, along with digital wheels which are respectively coupled to the print wheels are provided. The print wheels have type digits or numerals afiixed on the periphery thereof. A conventional servo system serves to position the first print wheel in response to an analog signal. Upon a print command signal, a digitizing pawl engages the digitizing wheel coupled with the first print wheel and the latter wheel is caused to rotate in a predetermined direction. As the first print wheel rotates in the. predetermined direction, the second print wheel is caused to rotate in proportion to the rotation of the first print wheel. After rotation of the first print wheel in the predetermind direction, which rotation is proportional to an increment of the analog input signal, the digitizing pawl associated with the first digitizing wheel engages the latter and stops the rotation thereof. At this time the second print wheel has rotated to a position substantially proportional to the increment of the said analog signal. A second digitizing pawl then engages the digitizing wheel associated with the second print wheel to accurately position the latter to a digital position. The first print wheel and the second print wheel are now in their proper positions and ready for printing a digital value corresponding to the input analog quantity. Printing may be accomplished by the provision of an inked ribbon, a paper tape and print hammers which all are operated in a conventional manner. Additionally, the analog input quantity may be recorded in analog form on the paper tape by the provision of a pen mechanism which is coupled with the first print wheel. l

Other features and objects of the invention will be better understood from a consideration of the following detailed description when read in conjunction with the attached drawings in which:

FIG. 1 illustrates a digital printer constructed in accordance with the teachings of the present invention;

FIG. 2 illustrates an alternative arrangement for the positioning of the second or units print wheel;

FIG. 3 illustrates the manner in which a pen mechanism may be coupled with the arrangements shown in FIGS.

1 and 2; and

FIG. 4 illustrates a paper tape or chart and the manner in which the digital and analog quantities may be recorded thereon.

Referring now to FIG. 1, a substantially conventional potentiometric servo system is shown including a servo motor 10, a potentiometer 11, a DC. voltage source 12, an amplifier 13, and input terminals 14 and 15. The servo motor 10 includes a winding 18 energized from an alternating current source (not shown), and control windings 19 and 20.

The input terminal 14 is connected to a movable arm 23 on the potentiometer 11. The input terminal 15 is connected to ground. The battery 12 is connected across the potentiometer 11, and one terminal 24 of the potentiometer 11 is connected through a line 25 to one input terminal of the amplifier 13. A second input terminal of the amplifier 13 is connected to ground. The output of the amplifier 13 is connected to a first terminal 27 of a switch 28 which includes a second terminal 29 and a movable arm 30. The movable arm 30 of the switch 28 is connected through a line 31 to one terminal of the control winding 19, and the second contact 29 of the switch 28 is connected through a line 32 to the juncture of the control windings 19 and 20. The remaining terminal of the control winding 20 is grounded.

The servo motor 10 includes an output shaft 36 which is coupled to a pulley 37. The pulley 37 is coupled with a belt or cord 38 which is arranged to drive pulleys 39 and 40. The pulley 39 is mechanically connected to the movable arm 23 of the potentiometer 11 as indicated schematically by the dashed line 41. Although a pulley and belt arrangement is shown for simplicity of illustration, it is to be understood that the drive should be positive. That is, the belt 38 should be sufficiently tight to prevent any slippage, or preferably the belt should have an end affixed to each of the pulleys 39 and 40, to ensure that the arm 23 and the shaft 45 are moved proportionately. Of course, positive type gearing may be employed between the shaft 36, the arm 23 and the shaft 45.

The servo motor 10 operates in a conventional manner to position its output shaft 36 in response to a variable input voltage applied to input terminals 14 and 15. Upon the application of an input voltage to the input terminals 14 and 15, the output shaft 36 of the motor 10 begins to rotate. As the shaft 36 rotates, the arm 23 of the potentiometer 11 is moved to a position at which the servo system rebal'ances and the shaft 36 ceases rotation. The pulley 40 also is rotated and in turn rotates a shaft 45 coupled thereto. A first print wheel 46 which may be termed a hundreds and tens print wheel is coupled to the shaft 45. A digitizing wheel 47 including a plurality of teeth 48 also is coupled to the shaft 45. Thus, the wheels 46 and 47 are rotated in accordance with the input voltage applied to the input terminals 14 and 15. The particular servo system shown in FIG. 1 is only exemplary and, if desired, other type servo systems may be employed.

The print wheel 46 includes type digits or numerals generally indicated by a reference number 49. Any desired number of type numerals may be affixed to the periphery of the print wheel 46. Generally it will be desirable to include one hundred type numerals, through 99. The number of teeth 48 on the digitizing wheel 47 corresponds to the number of type numerals on the print wheel 46. The teeth 48 are spaced apart a predetermined distance to define slots 50. The teeth 48 and slots 50 shown in FIG. 1 are approximately twice scale in relation to the digit spacing shown on wheel 46. The type numerals and teeth may be spaced entirely around the periphery of the wheels 46. and 47 or only on a segment thereof. Only a few of the type numerals are shown in FIG. 1.

A digitizing pawl 54 is positioned above the digitizing wheel 47 for engagement with the slots between the teeth 48. A solenoid 55 is coupled with the digitizing pawl 54 to urge the pawl into engagement with the periphery of the digitizing wheel 47 and into the slots thereon. The pawl 54 is in the raised position shown when the solenoid 55 is not energized. A print switch 56, which includes a button 57 adapted to short contacts 58 and 59, is connected with one terminal of a battery 60, the other terminal of which is grounded. The battery 60 and the switch 56 are connected in series with the solenoid 55 and a winding 62 of an electromagnetic clutch 63. The electromagnetic clutch 63 is selectively operable to couple the shaft 45 with a shaft 65.

A sector gear 66 is afiixed to the shaft 65, and the sector gear 66 normally is biased against a stop 67 by a spring 68. The teeth on the sector gear 66 engage the teeth on a pinion 70 which is affixed to a shaft 71. A sector of a print wheel 72 on which units type digits may be disposed is coupled to the shaft 71. Type digits 0-9 are included on the periphery of the print wheel 72. Additionally, a digitizing wheel 73 is coupled to the shaft 4 71, and this wheel includes a plurality of teeth 74 on it periphery equal to the number of numerals on the print -wheel 72. A units digitizing pawl 75 is disposed adjacent the periphery of the digitizing wheel 73.

The pawl 75 is rotated by a shaft which is spring coupled by a spring 81 to a shaft 82. The shaft 82 is rotated by an arm 83 which is operated by a solenoid 84. Print hammers 86 and 87 are coupled to the shaft 82. A tape or chart 90, such as a paper strip, is arranged to move in the direction of the arrow between the print wheels 46 and 72 and the hammers 86 and 87. In actual use, an inked ribbon (not shown) is positioned between the print wheels 46 and 72 and the tape 90. Conventional means for advancing the tape and ribbon are employed, but they are not shown for simplicity of illustration and because they do not form a part of the present invention. When the print hammers 86 and 87 strike the bottom of the chart 90, the numerals on the print wheels 46 and 72 directly above the chart 90 are printed on the chart. The pawl 75 is so positioned that it engage-s the digitizing wheel 73 and forces it to a digital position before the print hammers 86 and 87 strike the chart 90.

A switch 94 having contacts 95 and 96 and an arm 97 is mechanically coupled as indicated by a dashed line 98 with the digitizing pawl 54 and the arm 30 of the switch 28. Thus, the arms 30 and 97 of the respective switches 28 and 94 engage the respective lower contacts 29 and 96 when the solenoid 55 causes the pawl 54 to engage a slot on the periphery of the digitizing wheel 47. A battery 100 is connected between ground and the arm 97. The contact 96 is connected through a line 101 to a time delay circuit 102 which includes a series resistance 103 and a capacitor 104 which is connected to ground. The time delay circuit 102 is connected through a line 106 to the solenoid 84. When the arm 97 of the switch 94 engages the lower contact 96, the solenoid 84 is energized after a predetermined time delay. As will appear subsequently, the time delay allows the print wheels 46 and 72 to be positioned before printing. When the solenoid 84 is energized, the shaft 82 rotates in a counterclockwise direction causing the digitizing pawl 75 to engage a slot on the periphery of the digitizing wheel 73, followed by the print hammers 86 and 87 striking the bottom of the chart 90 to print the proper numerals.

Briefly, the digital printer illustrated in FIG. 1 operates as follows: the servo motor 10 positions the first or hundreds and tens print wheel 46 in accordance with the input voltage during which time the electromagnetic clutch 63 is de-energized and the output shaft 65 thereof does not rotate. The digitizing pawl 54 engages the periphery of the digitizing Wheel 47 and the servo motor 10 rotates the wheels 46 and 47 in a predetermined direction,'clockwise in the present example, until the pawl 54 drops into a slot 50, if it did not do so initially, and hits a tooth 48 on the Wheel 47. At the time the pawl 54 engages a slot on the periphery of the digitizing wheel 47, the electromagnetic clutch 63 is energized and the shaft 65 rotates in the predetermined direction with the shaft 45. As the shaft 65 rotates, the second or units print wheel 72 is positioned. The digitizing pawl 75 engages the digitizing wheel 73 and the print hammers 86 and 87 then cause the proper numerals to be printed. It should be noted that the gear ratios between shafts 65 and 71 are selected such that the wheel 72 may move through its complete range, 0 through 9, during rotation of the wheel 47 equal to a distance of one slot 50 and one tooth 48.

Considering the operation of the digital printer illustrated in FIG. 1 in greater detail, assume that the printer span is set for 100 volts, and assume that a DC. signal voltage, for example 10.4 volts, is applied to the input terminals 14 and 15. The servo motor 10 rotates the main shaft 45 in the manner explained previously to position the print wheel 46 such that the space between the numerals or digits 10 and 11 on the periphery of the print wheel 46 is opposite the print hammer 86. The print switch 56 is closed and the solenoid 55 and the winding on the electromagnetic clutch 63 are simultaneously energized. When the solenoid 55 is energized, the finger on the pawl 54 falls to the periphery of the digitizing wheel 47. Also, the arm 30 of the switch 28 engages the lower contact 29 thereby disconnecting the servo motor 16 from the amplifier 13 and shorting the control windings 19 and 20 of the servo motor. This action causes the servo motor to rotate the main shaft 45 in one predetermined direction, such as clockwise, until the finger on the pawl 54 engages a tooth 48 on the wheel 47, after which the servo motor 16 stalls. The teeth 48 on the digitizing wheel 47 are spaced such that the numeral 10 on the print wheel 46 is now opposite the print hammer 86.

During this time when the electromagnetic clutch 63 is energized, the output shaft 65 of the electromagnetic clutch 63 is rotated along with the main shaft 45. Thus, the shaft 65 rotates in a clockwise direction and thereby rotates the shaft 71 and the units print wheel 72 in a counterclockwise direction through the sector gear 66 and pinion 70. Normally the sector gear 66 is biased against the stop 67 by the spring 68 to maintain the units print wheel 70 in a position such that the digit 0 thereon is opposite the print hammer 87. As noted previously, the ratio between the sector gear 66 and the gear 78 is chosen so that rotation of the main shaft 45 corresponding to one space between teeth 48 on the digitizing wheel 47 moves the units print wheel 72 through an angle such that all numerals on its periphery travel past the print hammer 87. Thus, in the present example the main shaft 45 rotated an amount corresponding to 0.4 a space and tooth width on the digitizing wheel 47, and hence the units print wheel 72 was driven through 0.4 its travel and the number 4 is now opposite the face of the print hammer 87.

In case the numeral 4 is not exactly in the proper position, it will be properly positioned when the finger on the digitizing pawl 75 engages a space between the teeth 74 on the digitizing wheel 73. This operation occurs after a sufficient time delay (determined by the constants of time delay circuit 162) which allows the units print wheel 72 to move to at least its approximate position. When the digitizing pawl 54 moved into engagement with the digitizing wheel 47, the arm 97 on the switch 94 engaged the contact 96 to connect the battery 160 in series with the time delay circuit 102 and the solenoid 84. After the time delay, the solenoid 84 moves the arm 83 to cause the shaft 82 to rotate in a counterclockwise direction. The pawl 75 first engages a space between the teeth 74 on the digitizing wheel 73 to force this wheel to a digital position, followed by the printing hammers 86 and 87 striking the bottom of the chart 94 because of the action of the spring 81. The spring 81 is utilized in order to allow the print hammers 86 and 87 to freely strike the bottom of the chart 90 after the pawl 75 has engaged the digitizing wheel 73. If desired, the spring 81 may be omitted and the pawl 75 constructed of a flexible material. The only requirement is that the pawl 75 engage a space between the teeth 74 on the digitizing wheel 73 prior to the striking of the hammers 86 and 87.

Although the wheels 46, 47 and 72 are illustrated as being spaced substantially apart, in practice they are close together. In order to aid in close spacing, the digitizing wheel 47 may be affixed to the main shaft 45 between the pulley 40 and the print wheel 46. Additional print wheels may be utilized if desired. Although the print switch 56 is illustrated as being manually operable, it may be operated by a timing mechanism periodically, such as once each second. The print switch 56 may be periodically operated by a cam coupled with the driving mechanism employed for the tape 90.

FIG. 2 illustrates an alternative arrangement for positioning and digitizing the units print wheel 72. The apparatus illustrated in FIG. 2 is connected with the printer apparatus shown in FIG. 1 to the right of the line 2-2 in lieu of the components 63, 65, 66 and 70. The reference numeral 121 designates a portion of the housing for the digital printer upon which the elements shown in FIG. 2 are mounted. The shaft 45 shown in FIG. 1 extends through the housing 121 as illustrated in FIG. 2. A clutch disc 122 is afiixed to the shaft 45. A lever mechanism 123 including a support block 124, an electromagnet 125 and a lever 126 are all joined together and mounted on the shaft 45. The lever mechanism is freely movable with respect to the shaft 45. A collar 128 is affixed to the shaft 45 by means of a set screw 129 to maintain the lever mechanism 123 freely movable on the shaft 45. One end of the lever 126 is connected to a spring 132 and to a member 133, such as a chain, cord or belt. The belt 133 engages four freely rotatable pulleys 135 through 138. The opposite end of the belt 133 is connected with the spring 132 as shown. The belt 133 is wrapped around a sleeve and afiixed to a set screw 141 thereon. The set screw 141 also affixes the sleeve 140 to the shaft 71. The shaft 71 is coupled to the units print wheel 72 in FIG. 1. Thus, the belt 133 positions the shaft 71 and the wheels 72 and 73.

The digitizing pawl 75 is positioned adjacent to digitizing wheel 73 and is afiixed to the shaft 80 in the same manner as discussed in connection with FIG. 1. Additionally, the pawl 75 may be biased to a rest position against a stop 145 by a spring 146 connected to a stud 147. Studs 149 and 150 are provided to limit the travel of the lever 126.

The units positioning and digitizing mechanism illustrated in FIG. 2 operates in a similiar manner to the mechanism illustrated in FIG. 1 to position the units print wheel 72. The clutch disc 1-22 and shaft 45 rotate along with the hundreds and tens print wheel 46 in FIG. 1. When the print switch 56 in FIG. 1 is closed, the electromagnet 125 in FIG. 2 is energized and is attracted to the clutch disc 122. Thus, when the electromagnet 1 25 is energized, the lever mechanism 123 rotates in the predetermined direction (clockwise in the example given) with the clutch disc 122 and the shaft 45. As the lever mechanism 123 rotates, it positions the belt 133 which in turn positions the shaft 71 and the units print wheel 72 in FIG. 1. The digitizing pawl 75 operates in conjunction with the digitizing wheel 73 after a predetermined time delay to finally accurately position the units print wheel 72 as described in connection with the discussion of FIG. 1.

According to an additional feature of the present invention, the digital printer may include a pen mechanism such as that shown in FIG. 3 to provide an analog trace on the chart 90 in FIG. 1 in accordance with the magnitude of the input analog signal. A pen mechanism generally indicated by a reference numeral is operated from the shaft 45 of the digital printer. The pen mechanism 170 includes a pen 171 which is affixed to a pen positioning block 172. The pen extends through a sleeve 173 which is positioned within a hole in the housing 121. A supply tube 174 is connected with the pen 17-1 and an ink reservoir 175. A cord 178 passes around the upper portion of a mandrel 179 and a mandrel 180 and is affixed to and extended through the block 172. The cord 178 then extends around the lower portion of the mandrel 179 and is wrapped around the shaft 45 of the digital printer. The ends of the cord 178 are connected together with a spring 182. As the shaft 45 rotates, the cord 178 positions the block 172 which in turn positions the pen 17 1. As the pen 1741 is positioned, it draws an analog trace on the chart 90 in FIG. 1.

An example of the type of trace made by the pen 171 in FIG. 3 and the manner in which the numerals are printed on the chart 90 is illustrated in FIG. 4. FIG. 4 shows a portion of the chart 90 and digits which have been printed thereon by the print wheels 46 and 72. A trace 182 is drawn by the pen 171 in accordance with the position of the print wheel 46. Short pips 183 occur when digitizing takes place.

It should be noted that a visual read-out in digital form may be provided in addition to the indicia printed on the tape 90. Additional wheels may be provided which rotate along with the print wheels 46 and 72, and the former wheels may be arranged for viewing at all times. Additionally, electrical contacts and wipers may be coupled with the print wheels 46 and 7-2 and operated in synchronism therewith to provide an electrical output indicative of the printed output.

It now should be apparent that the present invention provides a digital printer which responds to analag signals and prints digits corresponding to the value of the analog signal. A first print wheel is positioned in accordance with the magnitude of the analog signal. A digitizing pawl engages the periphery of a digitizing wheel which is coupled with the print wheel, and the print wheel is moved in a predetermined direction until the digitizing pawl engages a tooth on the digitizing wheel. As the print wheel is moved in the predetermined direction, a second print wheel or sector thereof is positioned in accordance with the incremental movement of the first print Wheel. A second digitizing pawl engages a digitizing wheel coupled with the second print wheel to digitize a position of the second print wheel after which printing hammers are operated to print the digits corresponding to the value of the input analog signal. If desired, a pen mechanism may be coupled with the first print wheel to draw an analog trace corresponding to the position thereof and thus in accordance with the value of the input analog signal.

It will be understood that although exemplary embodiments of the present invention have been disclosed and discussed, other applications and structural and circuit arrangements are possible and that the embodiments disclosed may be subjected to various changes, modifications, and substitutions without necessarily departing from the spirit of the invention.

What is claimed is:

1. In a digital printer including servo means for receiving an input analog signal, a first print wheel, and means coupling the servo means with said first print wheel to move said first print wheel to a first position corresponding to the magnitude of said analog signal, the improvement comprising a first digitizing wheel having a plurality of teeth on the periphery thereof defining slots, the number of said teeth corresponding to the number of digits on said first print Wheel,

a first digitizing pawl arranged for selective engagement with a slot between the teeth on said first digitizing wheel,

a second print wheel,

coupling means for selectively coupling said second print wheel with said first print Wheel,

a second digitizing wheel coupled with said second print wheel and having a plurality of teeth on the periphery thereof defining spaces, the number of said teeth corresponding to the number of digits on said second print wheel,

a second digitizing pawl positioned for selective engagement with a space between the teeth on said second digitizing Wheel,

means coupled with said servo means for causing said servo means to move said first print wheel to a second position until said first digitizing'pawl engages a tooth on said first digitizing wheel, and

means for causing said coupling means to couple said second print wheel with said first print wheel for movement therewith as said first print wheel moves to said second position.

2. A device as defined in claim 1 wherein said coupling means includes an electromagnetic clutch coupled between said first print wheel and said second print wheel.

3. A device as in claim 1 wherein said coupling means includes an electromagnetic clutch coupled from said first print wheel to said second print wheel through gearing means.

4. A device as in claim 1 wherein said coupling means includes an electromagnetic clutch coupled between said first print wheel and said second print wheel through a lever means.

5. A device as in claim 4 wherein a pen mechanism means is coupled with said first print wheel and is positioned in accordance with the movement of said first print wheel.

6. In a digital printer including positioning means responsive to an input analog signal for positioning a first indicia-bearing printing means having digits thereon in response to said input analog signal, the improvement comprising a digitizing wheel having a plurality of teeth which define slots on the periphery thereof coupled with said first printing means,

a digitizing pawl arranged for selective engagement with the periphery of said digitizing wheel,

a second indicia-bearing printing means,

selectively operable coupling means for selectively coupling said second printing means with said first printing means whereby said second printing means may be moved through its complete range when coupled to said first printing means as said first printing means is moved an amount corresponding to one of said digits, and

means coupled with said positioning means and said digitizing pawl for causing said digitizing pawl to engage the periphery of said digitizing wheel, for causing said positioning means to move said first printing means until said digitizing pawl engages a tooth on said digitizing wheel and for causing said coupling means to couple said second printing means with said first printing means for movement therewith when said first digitizing pawl engages the periphery of said first digitizing wheel.

7. A digital printer as in claim 6 wherein said positioning means includes servo means for positioning said first printing means in response to said input analog signal,

said coupling means includes an electromagnetic clutch and gearing means coupled between said first and second printing means,

said first and second printing means have type digits atfixed to the periphery thereof, and

means coupled with said digital printer for causing digits on said printing means to be printed after said printing means have been positioned in accordance with the magnitude of said input analog signal.

8. A digital printer as in claim 7 wherein a pen mechanism is coupled with said first printing means and is positioned in accordance with the movement of said first printing means.

9. A digital printer as in claim 6 wherein said positioning means includes servo means for positioning said first printing means in response to said input anal-0g signal, and

said coupling means includes a clutch and a level mechanism coupled between said first and second printmg means.

10. In a digital printer including positioning means for receiving an input signal and positioning a first printing means in accordance with the magnitude of said input signal, the improvement comprising said printing means including a plurality of digits to be printed and a plurality of slots arranged thereon, first digitizing means arranged for selective engagement with one of said slots,

a second printing means,

coupling means for selectively coupling said first and second printing means,

second means including circuit means coupled with said positioning means and actuating means coupled with said first digitizing means for causing said first digitizing means to engage one of said slots and for causing said positioning means to move said first printing means until said first digitizing means arrives at one of said slots, and

said coupling means responding to said second means to couple said second printing means with said first printing means for movement therewith until said first digitizing means engages one of said slots.

11. A digital printer as in claim 10 including means responsive to said second means for printing selected indicia-of said first and second printing means after said first and second printing means have been positioned in accordance .With said input signal.

12. In a digital printer including a servo system means for receiving .an input analog signal and positioning an output shaft in accordance with the magnitude of said signal, a first print Wheel including type on the periphery thereof providing digits to be printed, first means coupling said shaft with said first print Wheel for positioning said first print Wheel in accordance with the position of said shaft, the improvement comprising a first digitizing Wheel having a plurality of teeth on the periphery thereof, said teeth defining slots therebetween,

a first digitizing pawl arranged for selective engagement with the slots between the teeth on said first digitizing wheel,

switch means coupled with said servo system means for selectively causing said shaft to rotate in a given direction,

second means coupling said first digitizing pawl with said switch means to operate said switch means as said digitizing pawl engages one of said slots,

a second print wheel having type on the periphery thereof for printing digits,

coupling means for selectively coupling said first and second print wheels, and

electrical means coupled with said first digitizing pawl and said coupling means for selectively operating said first digitizing pawl and said coupling means whereby said servo system means positions said first print Wheel in accordance with the magnitude of said input analog signal, said electrical means causes said digitizing pawl to engage a slot between the teeth on said first digitizing wheel, said switch means causes said shaft to rotate in a predetermined direction, and said electrical means causes said coupling means to couple said first and second print wheel so that said first print wheel moves to a position until said first digitizing pawl engages a tooth on said first digitizing Wheel and said sec-0nd print wheel moves in proportion to said first print Wheel as said shaft moves in said predetermined direction.

13. A digital printer as in claim 12 including selectively operable printing hammers for causing the digits on said first and second print Wheels to be printed after said first and second print wheels are positioned in correspondence with the magnitude of said input analog signal, and the digits printed are a digital indicia of the magnitude of said input analog signal.

References Cited by the Examiner UNITED STATES PATENTS 2,239,460 4/1941 Levy 346-98 X 2,807,664 9/1957 Klienberg et a1. 17823 2,880,410 3/1959 Postman 235-154 X 3,086,199 4/1963 Shimizu et a1. 235-164 X 3,201,794 8/1965 Simmonds et al. 34698 X ROBERT E. PULFREY, Primary Examiner.

E. S. BURR, Assistant Examiner. 

1. IN A DIGITAL PRINTER INCLUDING SERVO MEANS FOR RECEIVING AN INPUT ANALOG SIGNAL, A FIRST PRINT WHEEL, AND MEANS COUPLING THE SERVO MEANS WITH SAID FIRST PRINT WHEEL TO MOVE SAID FIRST PRINT WHEEL TO A FIRST POSITION CORRESPONDING TO THE MAGNITUDE OF SAID ANALOG SIGNAL, THE IMPROVEMENT COMPRISING A FIRST DIGITIZING WHEEL HAVING A PLURALITY OF TEETH ON THE PERIPHERY THEREOF DEFINING SLOTS, THE NUMBER OF SAID TEETH CORRESPONDING TO THE NUMBER OF DIGITS ON SAID FIRST PRINT WHEEL, A FIRST DIGITIZING PAWL ARRANGED FOR SELECTIVE ENGAGEMENT WITH A SLOT BETWEEN THE TEETH ON SAID FIRST DIGITIZING WHEEL, A SECOND PRINT WHEEL, COUPLING MEANS FOR SELECTIVELY COUPLING SAID SECOND PRINT WHEEL WITH SAID PRINT WHEEL, A SECOND DIGITIZING WHEEL COUPLED SAID SECOND PRINT WHEEL AND HAVING A PLURALITY OF TEETH ON THE PERIPHERY THEREOF DEFINING SPACES, THE NUMBER OF SAID TEETH CORRESPONDING TO THE NUMBER OF DIGITS ON SAID SECOND PRINT WHEEL, A SECOND DIGITIZING PAWL POSITIONED FOR SELECTIVE ENGAGEMENT WITH A SPACE BETWEEN THE TEETH ON SAID SECOND DIGITIZING WHEEL, MEANS COUPLED WITH SAID SERVO MEANS FOR CAUSING SAID SERVO MEANS TO MOVE SAID FIRST PRINT WHEEL TO A SECOND POSITION UNTIL SAID FIRST DIGITIZING PAWL ENGAGES A TOOTH ON SAID FIRST DIGITIZING WHEEL, AND MEANS FOR CAUSING SAID COUPLING MEANS TO COUPLE SAID SECOND PRINT WHEEL WITH SAID FIRST PRINT WHEEL FOR MOVEMENT THEREWITH AS SAID FIRST PRINT WHEEL MOVES TO SAID SECOND POSITION. 